Process for the formation of shaped trioxane structures and polymerization thereof



United States Patent 3,231,543 PROCESS FOR THE FORMATION OF SHAPEDTREOXANE STRUCTURES AND POLYMERI- ZATION THEREOF Saunders Eliot Jamison,Summit, N1, assignor to Celanese Corporation of America, New York, N.Y.,a corporation of Delaware No Drawing. Filed Oct. 14, 1960, Ser. No.62,534 3 Claims. (Cl. 260-67) This invention relates to shaped,self-supporting structures extended in no more than two dimensions andto processes for making such structures from solidifiable -mon0mers.

fibrous material or self-supporting films by a process which avoidsthermal degradation of the fiber or film forming polymer. Other objectswill appear hereafter.

The object of this invention is achieved by a process for the formationof shaped, self-supporting structures extended in no more than twodimensions which comprises polymerizing a solid phase monomer in theform -of said shaped, self-supporting structure in the presence of afluid catalyst.

This invention is particularly applicable to the polymerization oftrioxane and for convenience will be described with reference thereto.

In a preferred embodiment of this invention, trioxane is admixeduniformly with a resinous binder, extruded through a spinning orifice toform a stream and then polymerized in the presence of gasiform boronfluoride after solidification of the stream. solidification of thestream to a self-supporting structure makes the invention applicable tomonomers which cannot be polymerized instantaneously.

The resinous binder serves the dual function of increasing the viscosityof the trioxane-to permit it to be extruded in a fine stream and ofmaintaining the trioxane in a fibrous structure while polymerizationtakes place.

In most cases, it is desired to eliminate the resinous binder afterpolymerization is complete so that the fibrous residue will have thecharacter of the oxymethylene polymer. This may be achieved by theselection of a pears after lending its structure to the polymerizationprocess.

When an oxymethylene polymer fiber is desired, the resinous binder isblended with trioxane in proportions between about 5 and 50 weightpercent, based on the weight of trioxane. The binder is preferablydissolved in molten trioxane before extrusion thereof through thespinning orifice. If desired, both the trioxane and the binder may bedissolved in a common solvent to form a viscous solution and thesolution may be extruded through the spinning orifice.

Solidification of the extruded stream is by cooling in the case where nosolvent is used and usually by cooling and evaporation where a solventis used. Volatile solvents and mild evaporative conditions are used withtri- "ice oxane to control the trioxane loss which would otherwise occurbecause of the high volatility of the trioxane.

In some cases wet spinning methods may be used wherein the solution isextruded into a non-solvent liquid, such as n-octane, as a coagulant. Insuch cases the filaments may be polymerized in the presence of a liquidphase catalyst, such as boron trifluoride in solution in the coagulantliquid. Alternatively, the filaments may be removed from their liquidcoagulant environment before polymerization in the presence of agasiform catalyst takes place.

Suitable resinous binders for trioxane include thermoplastic vinylpolymers such as polyvinyl acetate, polystyrene, polyvinyl chloride,polymethyl methacrylate, polyvinyl pyrrolidone, polyethyl acrylate andpolyvinyl caprolactam; thermoplastic condensation polymers, such asrelatively low melting polyamides and polyesters; and thermoplasticcellulosic derivatives, such as cellulose acetate and ethyl cellulose.

Polyacetaldehyde, prepared by acid-catalyzed polymerization ofacetaldehyde at its freezing point and of the formula is a useful bindersince it depolyrnerizes readily when exposed to a trioxanepolymerization catalyst under polymerization conditions.

The nature of the common solvents used when dry spinning is desired isdependent on the nature of the resinous binder. For many binderstrioxane solvents such as methylene chloride or acetone are suitable.Suitable spinning compositions of this type include from 10 to weightpercent of binder and from 50 to 500 Weight percent of solvent per unitweight of trioxane.

Spinning conditions depend upon the nature and proportion of theresinous binder and the nature and proportion of solvent if any. Thespinning orifice diameter may vary as desired according to the productdesired. Spinning temperatures from about 0 C. to about 100 C. aresuitable for most spinning compositions.

After the extrusion operation is completed, the extruded stream issolidified, preferably byvcooling or by cooling and evaporation. Theatmosphere into which the spinning composition is extruded is preferablymaintained at a temperature between about 50 C. and 50 C.

The preferred gasiform. catalyst is boron trifiuoride. It is preferablymaintained in the atmosphere surrounding the solidified trioxane-binderfilament at a concentration of from about 1 to 100 weight percent.Vaporizable acidic boron trifiuoride complexes may also be used. Asuitable catalyst environment may be maintained by passing nitrogenthrough a normally liquid boron trifluoride complex and thereafter intothe polymerization zone.

Suitable liquid phase catalysts include solutions of boron trifiuorideor of acidic complexes of boron trifiuori-de in liquids, which arenon-solvents for the trioxane and resinous binder under thepolymerization conditions.

Polymerization temperatures are suitably between about -50 and 60 C. andthe period of reaction may vary from about 12 hours to 1 minute. In mostcases the catalytic environment is maintained just beyond the spinningorifice so that polymerization proceeds as soon as the extruded streamis solidified to a self-supporting structure. It is possible thatpolymerization is initiated to a minor extent before solidification butby far the greater portion of the trioxane solidifies before beingpolymerized.

In some cases, it may be desirable to prepare filamentary materialhaving characteristics intermediate between those of the oxymethylenepolymer and those of the resinous binder. In such cases the resinousbinder is not removed after polymerization and the amount used dependsupon the desired characteristics of the final product.

In another advantageous aspect of this invention a cross-linkedpolymeric structure may be prepared by the copolymerization of trioxanewith a polyfunctional comonomer and particularly a polycyclic ether,such as a polyepoxide. such cross-linked copolymers since a usefulfilamentary material is produced by the polymerization reaction andthere is no necessity for further shaping of the intractable polymer.

Among the suitable polyepoxides which may be used are the diepoxides ofhydrocarbon dienes, such as vinyl cyclohexene dioxide anddicyclopentadiene dioxide; and diepoxides of substituted hydrocarbondienes, such as 3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexanecarboxylate. Polymeric epoxides, such asthe epoxy resins produced by the reaction of epichlorohydrin with abisphenol may also be copolymerized with trioxane by the method of thisinvention. Other polycyclic ethers include diketals and diacetals ofpentaerythitol and dioxetanes formed from pentaerythitol and itsderivatives. It may be noted that polyvinyl pyrrolidone and polyvinylcaprolactam, mentioned above as resinous binders are also polyfunctionalcomonomers capable of interaction with trioxane in a copolymerization.

The polycyclic ethers are suitably blended into the spinningcompositions in proportions between about 10 and 50 weight percent,based on the weight of trioxane. Spinning and polymerization conditionsare as described above.

In the copolymerization reaction, trioxane rings open to produce shortchains of three oxymethylene units and the epoxy rings open to producesubstituted oxyethylene units. These units link up to form a spacepolymer comprising chains of oxymethylene units interspersed withoxyethylene units said chain being cross linked across carbon atoms ofsaid oxyethylene units.

While the invention has been described with respect to thepolymerization of spun structures, it is to be understood that otherfibrous structures may be polymerized. For example, filaments may beprepared by drawing the viscous mixture from a softened and sticky meltthereof. Fibrous trioxane strands may also be prepared by sublimationunder carefully controlled conditions, as described below in Example I.While it is preferred to polymerize filamentary monomer other fibrousforms of monomer may be polymerized. Fibrous monomers having an extendeddimension of at least 100 times the other two dimensions are suitable.Similarly monomers in film structures wherein each extended dimension isat least 100 times the thickness are suitable. 1 r

If desired, the trioxane may be copolymerized with from 0.4 to 40 weightpercent of ethylene oxide or dioxolane. Such copolymers have greaterthermal stability than homopolymers. Since the shaping of the polymerafter its formation is not required, in accordance with this invention,high thermal stability is often not essential. But where it is desiredsuch copolymers may be prepared by forming filaments from a mixture oftrioxane, comonomer and binder and polymerizing as described above.

While the invention has been described with reference to thepolymerization of trioxane, the general technique is also applicable toother normally solid or s-olidifiable monomers. The technique isparticularly applicable to cationically catalyzed vinyl monomers and tocyclic compounds in which at least one ring bond is highly polarizablebecause of the presence of an electro-negative heteroatom. Examples ofthe cyclic compounds include other cyclic ethers, lactones, acetals,ketals, sulfides, imines and lactams. Examples of vinyl monomers includeolefins, cycloefins, vinyl ethers and acrylic acid derivatives. It ispreferred that the monomer have a molecular weight not higher than about300.

This invention permits the utilization of V Example I A fibroussublimate of trioxane was prepared by a sequence of two condensationoperations. In the first, molten trioxane was heated in a vessel coveredwith a watch-glass in such a manner that the trioxane vaporized in thevessel and condensed as a closely packed snow on the under surface(convex) of the watch glass. The temperature of the watch glass couldnot rise above the melting point of trioxane (64 C.) for thecondensation. The watch glass was cooled, by directing a cool air streamon the upper (concave) surface of the watch glass. Satisfactory rates ofcollection were maintained without boiling the trioxane (heating range-100 C.).

In the second condensation the watch glass with the trioxane snowattached to its lower (convex) surface was placed over another vesselwhich was kept cool (room emperature). A stream of warm air (55-60 C.)was directed at the upper (concave) surface of the watch glass so as toheat the trioxane without melting it. The trioxane then sublimeddownward into the vessel where it formed a voluminous fibrous network.

A portion of the above-described fibrous mass was inserted into astoppered test tube and sufficient boron tri fiuoride to provide aconcentration in the test tube of 3 volume percent was thereafterintroduced. The tube was maintained at 25 C. for a period of 150minutes. The contents of the tube were then washed with acetone toremove unreacted trioxane and boron trifiuoride. The polyoxymethylenefibers corresponded in weight to 71% of the trioxane starting material.

Example II 25% solution of polyvinyl acetate in trioxane was extruded atC. through a 2.0 mm. orifice into a chamber held at 50 C. from which itwas taken up at room temperature on glass tube. The filaments thusprepared were exposed for 30 minutes in a test tube at room tempera=ture to an atmosphere of dry nitrogen containing about 20 volume percentof boron trifiuoride. After exposure the filament was washed extensivelywith warm water to remove unreacted trioxane. Analysis showed that thefilament had a composition of 47% polyoxymethylene and 53% polyvinylacetate.

Example III Polyacetaldehyde was obtained by polymerizing acetaldehydeat its freezing point (123.5 C.). Acetaldehyde 392 parts by weight) wasdistilled into a cold trap maintained at its freezing point andcontaining 0.22 part of boric acid. Upon completion of the distillation,1.45 parts of polymer was recovered having an inherent viscosity of 3.0(0.1% solution in acetone at 25 C.).

Strands were drawn with a glass rod from a 10% solu tion of thispolyacetaldehyde in trioxane. The strands were exposed at roomtemperature for 30 minutes to an atmosphere of volume percent of borontrifluoride. After washing with water, analysis showed that the polymerfilaments were pure polyoxymethylene.

Example IV Strands were drawn with a glass rod from a solution (at75-80" C.) consisting of 10 parts of trioxane, 2.5 parts of' polyvinylacetate and 1 part of a diepoxide of the group listed below. The strandswere exposed at: room temperature to boron trifluoride inconcentrations: ranging from 13% to 100% by volume (in nitrogen) forriods of two hours at room temperature. The mate-- rial was then Washedwith boiling dimethylformarnide to remove all material other than thecrosslinked polymer- The results are shown in Table 1, below.

e3,4-epoxy-6-methyl-cyclohexylenethyl-Ii,4-epoxy-6-methyl-cyclohoxanecarboxylate.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis:

1. A process for the formation of a shaped, self-supporting structureselected from the group consisting of filaments and films whichcomprises forming a solid phase monomer comprising at least 50% oftrioxane into said shaped, self-supporting structure, and polymerizingsaid monomer in the presence of a fluid trioxane polymerizationcatalyst.

2. A process for the formation of fibrous material from a monomercomprising at least 50% of trioxane which comprises forming said monomerinto a solid structure in filamentary form and polymerizing said monomerin said structure in the presence of a gasiform trioxane polymerizationcatalyst.

3. A process for the formation of fibrous material from trioxane whichcomprises forming trioxane into a solid 6 trioxane in said structure inthe presence of gaseous boron trifluoride.

References Cited by the Examiner UNITED STATES PATENTS 2,170,439 8/ 1939Wiezevich 18--57 XR 2,519,550 8/1950 Craven 260-340 2,806,015 9/1957Kern.

2,822,237 2/ 1958 Iwamae 1854 2,840,447 6/ 1958 Green 1854 2,864,82712/1958 Baer et a1 260--340 2,883,361 4/1959 Handy et a1.

2,890,191 6/ 1959 Edmonds 260-30.4 2,891,837 6/1959 Campbell 18542,913,430 11/1959 Roeser 26030.4 2,934,528 4/ 1960 Lundberg 26088.32,947,727 8/1960 Bartz 26067 2,947,728 8/1960 Bartz 260 -67 2,947,7368/1960 Lundberg 26088.3 2,989,506 6/ 1961 Hudgin et al 26067 2,989,5106/1961 Bruni 26034 XR 2,989,511 6/1961 Schnizzer 260-67 OTHER REFERENCESDAlelio: Fundamental Principles of Polymerization, John Wiley & Sons,Inc., New York (1952), and Chapman & Hall, Ltd., London, p. 192.

WILLIAM H. SHORT, Primary Examiner.

WILLIAM J. STEPHENSON, NICHOLAS S. RIZZO,

Examiners.

J. W. GERIAK, A. B. ENGELBERG, C. B. HAM- BURG, I. TOVAR, E. M.WOODBERRY,

Assistant Examiners.

1. A PROCESS FOR THE FORMATION OF A SHAPED, SELF-SUPPORTING STRUCTURESELECTED FROM THE GROUP CONSISTING OF FILAMENTS AND FILMS WHICHCOMPRISES FORMING A SOLID PHASE MONOMER COMPRISING AT LEAST 50% OFTRIOXANE INTO SAID SHAPED, SELF-SUPPORTING STRUCTURE, AND POLYMERIZINGSAID MONOMER IN THE PRESENCE OF A FLUID TRIOXANE POLYMERIZATIONCATALYST.